I have had the same issue with the recent template update on mobile devices. Burger menu shows active “X” but no menu appears. If you begin scrolling down the page, the menu will ultimately appear after about half a page of scrolling. It would appear to be a reveal issue. I am using Chrome on an LG G6 running Android 7.0. I have cleared the cache and browser history. Here is a screenshot showing the “X” but no menu:
Thank you for assistance in fixing this issue.